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A001748 a(n) = 3 * prime(n). 41

%I #66 Feb 05 2024 00:52:42

%S 6,9,15,21,33,39,51,57,69,87,93,111,123,129,141,159,177,183,201,213,

%T 219,237,249,267,291,303,309,321,327,339,381,393,411,417,447,453,471,

%U 489,501,519,537,543,573,579,591,597,633,669,681,687,699,717,723,753

%N a(n) = 3 * prime(n).

%C Semiprimes divisible by 3. - _Jianing Song_, Oct 02 2022

%H Paolo P. Lava, <a href="/A001748/b001748.txt">Table of n, a(n) for n = 1..20000</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/Skeleton.html">Skeleton</a>

%F A164023(a(n)) = A164024(a(n)) = A000040(n). - _Reinhard Zumkeller_, Aug 09 2009

%F a(n) = 3*A000040(n). - _Omar E. Pol_, Jan 31 2012

%F A253046(a(n)) < a(n). - _Reinhard Zumkeller_, Dec 26 2014

%t Prime[Range[22]]*3 (* _Vladimir Joseph Stephan Orlovsky_, Apr 29 2008 *)

%o (PARI) 3*primes(22) \\ _Charles R Greathouse IV_, May 19 2011

%o (Magma) [3*p: p in PrimesUpTo(300)]; // _Vincenzo Librandi_, Mar 26 2014

%o (Haskell)

%o a001748 = (* 3) . a000040 -- _Reinhard Zumkeller_, Dec 26 2014

%Y Subsequence of A001358.

%Y Cf. A000040, A100484, A253046, A164023, A164024, A179545, A253046.

%K nonn,easy

%O 1,1

%A _N. J. A. Sloane_

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Last modified March 28 08:12 EDT 2024. Contains 371236 sequences. (Running on oeis4.)